青藏高原东缘表土有机碳同位素分布特征及其主控因素研究

发布时间：2018-04-21 19:57

  本文选题：有机碳同位素 + 表土　； 参考：《中国地质大学(北京)》2017年博士论文

【摘要】：土壤有机碳同位素与地表植被组成密切相关,受控于环境要素。通过研究表土有机碳同位素组成和现代植被群落、气候之间的关系可以为古气候研究提供理论基础,同时为定量重建古气候和估算高原隆升幅度提供参考资料。本项目在青藏高原东缘海拔588-4846m采集表土测试有机碳同位素,并将其与青藏高原东缘现代植被群落组成、气象要素资料进行综合研究,以探讨不同海拔高度表土有机碳同位素变化规律并分析其控制性因素。通过研究发现,青藏高原东缘表土有机碳同位素组成总体随着海拔的上升呈先下降而后上升的变化趋势:碳同位素值在2000m以下不稳定并随海拔上升而下降,在2000m以上随海拔升高逐渐稳定上升,在3000-3500m再次不稳定并随海拔的上升呈下降趋势,3500m以上随海拔升高而稳定上升。表土有机碳同位素组成在不同植被地带内有差异,按照常绿落叶阔叶混交林(平均-27.28‰)—常绿阔叶林(平均-27.25‰)—亚高山灌丛草甸(平均-25.85‰)—亚高山针叶林(平均-25.81‰)—高山灌丛草甸(平均-25.16‰)—干旱河谷植被(平均-24.07‰)的顺序,表土有机碳同位素变重。常绿落叶阔叶混交林、高山灌丛草甸地带内的表土有机碳同位素值随海拔上升而上升,常绿阔叶林、亚高山针叶林、亚高山灌丛草甸地带内的表土有机碳同位素值随海拔上升呈先下降而后上升的趋势,干旱河谷灌丛地带内表土有机碳同位素组成与海拔高度没有相关关系,但在同一河谷区内随海拔升高呈下降趋势。不同海拔高度、不同植被地带下土壤有机碳同位素变化的差异主要是由C3、C4、CAM植物比例变化和C3植物生理调整引起的。C4、CAM植物比例的下降是导致碳同位素下降的主要原因。当C3、C4、CAM植物比例稳定时,C3植物生理调整的控制作用才能显现出来,导致碳同位素的上升。气温、降水对C4、CAM植物的分布具有决定性的作用,此外,光照也发挥了重要作用,但其作用海拔范围有限。气温对C3植物生理调整的控制作用是明确的,而降水和气压的控制作用相对较小。在缺乏适宜的气温、降水环境下,仅靠气压变化无法导致土壤有机碳同位素的强烈变化。本文通过与前人研究成果结合建立了青藏高原周缘地区表土有机碳同位素与海拔之间的回归方程,以期为后人在青藏高原地区开展古气候古环境研究提供参考。
[Abstract]:Soil organic carbon isotopes are closely related to the composition of surface vegetation and are controlled by environmental factors. By studying the organic carbon isotopic composition of topsoil and modern vegetation communities, the relationship between climate can provide a theoretical basis for paleoclimate research, and provide reference for quantitative reconstruction of paleoclimate and estimation of uplift range of plateau. Organic carbon isotopes were collected and tested at 588-4846m above sea level in the eastern margin of Qinghai-Xizang Plateau, and combined with modern vegetation community composition and meteorological data of the eastern margin of Qinghai-Xizang Plateau. The variation of organic carbon isotopes in topsoil at different elevations was discussed and its controlling factors were analyzed. It is found that the total organic carbon isotopic composition of the surface soil in the eastern margin of the Qinghai-Xizang Plateau decreases first and then increases with the increase of altitude: the carbon isotope value is unstable below 2000m and decreases with the rise of altitude. When the altitude is above 2000m, it will rise steadily with the increase of altitude, and will be unstable again at 3000-3500m and will decrease with the rise of altitude, and will rise steadily with the increase of altitude. The organic carbon isotopic compositions of topsoil are different in different vegetation zones. According to the evergreen deciduous broad-leaved mixed forest (mean -27.28 鈥，

本文编号：1783886